power main transformer
power main transformer

We use transformers in a wide range of residential and industrial applications. They help improve the security and efficiency of power systems by raising or lowering voltage levels as required. In a world highly reliant on electrical systems, it is important to know how these devices work.

This article by Daelim will discuss one specific type, the main power transformer, to guide you in electrical systems.

Daelim is a leading Chinese brand for electrical components and solutions. If you’re looking for quality, well-made products that can deliver impressive results, you should check them out.


Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Dry-type Transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva


What is the Main Power Transformer?

The main power transformer is a device used to change the AC voltage using electromagnetic induction means. It has a main member or the primary coil, the secondary coil, and a core. 

The function of this transformer includes voltage conversion, current conversion, impedance transformation, isolation, and regulation.

The industry divides transformers into plenty of other types to suit different transformer functions.

Selection of Power Distribution Main Transformer in 110kV Substation Design

Main Power Transformer
Main Power Transformer

Common Electrical Transformer Types and Their Function

Though all follow the same principles, the construction of transformers has different methods. There are several types of transformers used in the electrical power system. We can classify transformers by voltage levels, core medium, winding arrangement, use and installation place, etc.

Below we discuss different types of transformers and their purpose.

Selection and Capacity Calculation of Transformers Used in Substations

Transformer Types Based on Voltage Transformation

These are the most common transformer types used in the industry for all applications. They’re categorized as step-up and step-down transformers, depending on the voltage ratio from the primary to secondary windings.

Step-Down Transformer

This transformer type converts the primary voltage level to a lower voltage across the secondary output. You can achieve this output by the ratio of primary and secondary windings. For step-down transformers, the amount of windings is higher across the first side than the secondary side. Therefore, overall, the winding ratio remains more than 1.

Professionals use step-down transformers to convert high voltages to low voltages in an electrical distribution system. They reduce the cost and loss of electricity and provide a long-distance power delivery solution.

Selection of 500kV Main Transformer in Hydropower Station

Main Power Transformers
Main Power Transformers

Step-Up Transformer

Step-up transformers are just the other step-down transformers. It increases the low primary voltage to a high secondary voltage. For the Step Up transformer, the ratio of the primary and secondary winding remains less than 1. That means there are more turns in the secondary winding than in the primary.

Electricians use step-up transformers in stabilizers and inverters where low voltage is converted to a much higher voltage. Furthermore, it is in high demand in an electricity distribution grid. Power distribution-related applications require high voltage to function efficiently.


set up transformer
set up transformer

Transformer Types Based on Core Design

Transformer type is determined by the medium between the primary and secondary winding. Air core transformers are great for light loads, while iron core transformers can handle heavy loads.

Three-Winding Transformer | Three-Phase Transformer

Air-Core Transformer

The air-core transformer does not require a physical magnetic core. Instead, it uses the air to provide its flux linkage.

Faraday’s law of induction states that a magnetic field will cause induction in a coil placed inside a magnetic field. Using an air-core transformer, the primary coil produces an alternating current, which induces a voltage in the secondary coil. This reaction then powers the load.

Power Transformer Core
Power Transformer Core

Iron-Core/ Ferrite core Transformer

Ferrite cores are ferromagnetic materials that have high magnetic permeability. Professionals use them to reduce losses in high-frequency applications because of this property. Furthermore, they are prominent devices in switch-mode power supply (SMPS) and other digital circuitry.

Ferrite core transformers also offer different types of shapes and sizes, counting on the appliance requirement. It is more common in electronics rather than electrical applications. The most popular shape in the ferrite core transformer is the E core.

Transformer Types Based on Winding Configuration

Their winding order classifies the transformers, usually the number of individual windings around the core. One of the types is Auto Winding Transformers, which are very popular.

What are the types of transformer windings ? What are the types of concentric windings?

Two-Winding Transformer

This transformer has two windings, one for the input and one for the output. The input is an AC power source, while the second is connected to a load. These are electrically isolated but magnetically coupled.

Changing magnetic flux causes the current to produce the induced EMF within the secondary winding. This voltage is simply because of induction. The voltage is mostly based on the windings ratio, but it can raise or lessen the input voltage.


The center-tapped node is movable in auto-winding transformers while the primary and the secondary coil are connected in series. Depending on the center-tapped position, you can change the secondary voltage.

How to Install a 500kV Main Transformer?

Transformer Types Based on Function

This section discusses transformers based on their role in an electrical system.

Power Transformer

Power transformers are large and powerful, transmitting high voltage power from generators to distribution centers. Their size and insulation make them perfect for all kinds of power generation stations and transmission substations.

power transformer solutions for oilfields

Distribution Transformers

Professionals use these transformers for power distribution to remote locations. These devices are for the distribution of electricity at low voltage.

Voltages can be less than 33KV for industrial purposes and 440v-220v for domestic purposes.

Several factors determine the type of distribution transformer you need, such as:

  • mounting design
  • insulation type
  • number of phases
  • voltage class
  • and BIL or Basic impulse levels.

Distribution Transformer Selection of An Office Building

Measurement Transformer

A measurement transformer is a device that allows for the measurement of power. Electricians use this instrument to measure the phase, current, and voltage of the actual power line.

Potential Transformer

The potential transformer has two coils, one on the primary side and one on the secondary side. The primary coil is connected to the HV line. Meanwhile, the secondary coil is connected to all other meters and instruments used to measure electricity.

The transformer uses the primary winding to decrease the voltage level to a certain limit, otherwise known as a point. This model has a grounded secondary winding which functions to protect the circuit from electrical shock.

Three phase Dry-type Isolation Transformers

Current Transformer

The current transformer is a measuring instrument that acts as a high-current transformer. Once it senses a situation where the current in the circuit is too high, it uses transformers to lower the current and send it to the desired value in the circuit.

There are three types of current transformers: wound, toroidal, and bar type.

Selection of Power Distribution Main Transformer in 110kV Substation Design

Wound Current Transformer

We can connect the primary winding of the transformer in series physically by using the conductor. This conductor then carries the measured current within the circuit. The secondary current is mainly dependent on the transformer’s turns ratio.


This transformer doesn’t have a primary winding and instead has a hole through which the current flows. Some of them also have an internal split-core that allows for easier installation and removal.

Bar Type

This transformer uses the bus bar of the major network like the primary winding. Furthermore, it is protected from the high voltages of the network and generally bolted toward the device which carries current.

How to choose and install rural distribution transformers

Transformer Types Based on Phase Design

Phase design is the wiring principle which the transformers use to transform electricity. There are two popular phase designs which are single-phase and three-phase transformers.

Single-Phase Transformer

The working principle of a transformer is to create an alternating current by converting electrical energy into mechanical torque. A single-phase transformer creates AC power using two windings, primary and secondary. The primary winding provides the AC supply, whereas the load is connected to the secondary winding.

Electric Pole Transformer | Single Phase Transformer

37.5kva single phase transformer
Single Phase and Three Phase Pad-mounted Transformer From Daelim
Single Phase and Three Phase Pad-mounted Transformer From Daelim

Three-Phase Transformer

Meanwhile, the three 1-phase transformers function by connecting them using three primary windings. You can also connect their three secondary windings like one secondary winding. This configuration creates the 3-phase supply, which is prominent in generating, distributing, and transmitting electric power.

The assemblage of this transformer is not expensive, and the connection works through Star and Delta type.


Standard Configuration and Parts Of A Transformer

You should note that transformers do not generate electrical power but simply convert it. Below are the key parts of a transformer and their function:

Input Connection

The input side of the transformer is called the primary. It is where the main electrical power to transform connects.

Output Connection

The output side of the transformer is where the power is sent to the load. Depending on demand, the incoming electric power will either be increased or decreased.


Transformers have two windings that either deliver or receive power. The primary winding is the coil that sends power to the load. Meanwhile, the secondary winding is the coil that receives power from the source. Manufacturers subdivide these two coils into several smaller coils to reduce flux creation.


The transformer core provides a controlled path for the magnetic flux generated in the transformer. The core is made of many thin laminated steel sheets. This design allows for cooling by using fewer materials.

We can find two main types of windings in a transformer: the core-type and the shell-type. Core-type windings surround the laminated core, while shell-type windings are inside the laminated core.

What Is In A Power Transformer?

A power transformer is an electrical device experts use to transfer power from one circuit to another. It doesn’t change the frequency, and it can provide several different AC supplies at various voltages. Power transformers have a main member or the primary coil, the secondary coil, and a core.

Power Transformer: The Ultimate FAQ Guide

What Is The Main Use Of A Transformer?

Transformers allow the flow of electrical energy from one circuit to another and transform its voltage. Professionals employ electric circuits to change the current flow, voltage, and electromotive force depending on the current direction.


What Is The Most Common Transformer Configuration?

Laminated core transformers are the most common type of transformer used in power transmission and appliances, converting input voltage to low voltage to power electronic devices.

Daelim has been in the transformer business for over a decade and is one of the most trusted brands. With a reputation for high-quality transformers, it’s your go-to brand when looking for something reliable.

If you’re looking for electrical products and solutions, Daelim Belefic is your innovative and reliable partner. From main power transformers to other electrical transformer types, Daelim has it all. Contact Daelim today to learn more.


About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. As a expert, I am glad to share my experience in transformer to you. I believe our professional team can always provide you with high quality service and we are ready to provide you with one stop solution. If you have problems when you are looking for the equipment, what you need to do is tell us.


Daelim currently has 69KV class, 138kv class, and 220kv class main power transformers.
If you find that these main power transformers cannot meet your requirements, you can tell us your requirements and we can provide you with customized services. Our main power transformer has been applied in more than 20 countries all over the world.

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